SPRING NATURE STUDY. 603 



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of the work of leaves in breathing and in making food for 

 the plant. 



Make sure that the children discover by observation the 

 importance of sunlight to the leaves, the way in which they 

 twist and turn and stretch to get the sunlight, and the effect 

 of keeping leaves where they cannot get sunlight. 



The Leaves as Breathing Organs. Begin the study of 

 breathing by leading the children to see and tell how ne- 

 cessary breathing is for them. Let them see what is the 

 effect of " holding their breath " and of breathing the air 

 in a paper bag held tightly over mouth and nose. Tell the 

 children that the lungs are two bags, with thousands of 

 smaller bags or sacks opening into them (illustrate with 

 paper bag), thus making a very large surface very much 

 crumpled (like a paper bag compressed into a small space), 

 that the walls of these sacs are full of blood vessels, and 

 that the blood takes in the air from the bags, and throws 

 out the poisonous gases of the body. 



The leaves are to plants what the lungs are to the chil- 

 dren. Each leaf is like one of these little sacs ; but instead 

 of being in the plant, as our lungs are in the body, it is 

 outside, somewhat as if our lungs with all their sacs might 

 be turned'" inside out." Each leaf has a network of veins 

 and thousands of little " breathing-pores " too small to be 

 seen by the eye, through which the useful gases, or benefi- 

 cial parts of the air, pass into the leaf, and the injurious 

 gases in the leaf pass into the air ; that is, the leaves 

 breathe in oxygen, and breathe out carbonic oxide (com- 

 monly called carbonic acid), much as we do. 



The Leaves as Factories. The papers given below, writ- 

 ten by third-grade children, show that they can get fairly 

 clear ideas of the work of the leaves in manufacturing 

 plant food or in making starch and sugar. 



Lead the children to tell about some factory, dwelling on 



